Shock-absorbing implant for use in shoulder arthroplasty

ABSTRACT

A shock-absorbing implant for use in shoulder arthroplasty has a bearing surface, a mounting base affixed to or formed with the bearing surface, a convex element extending outwardly of the mounting base opposite the bearing surface, a receptacle positioned so as to slidably or pivotably receive a portion of the convex element therein, a housing receiving at least a portion of the receptacle therein, and a resilient element received in the housing and bearing against a surface of the housing and against a surface of the receptacle. The bearing surface can be concave when the implant is used as a glenoid implant. The bearing surface can be convex when the implant is used as a humeral head implant.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. patent applicationSer. No. 14/082,855, filed on Nov. 18, 2013 and entitled“Shock-Absorbing Humeral Implant for Shoulder Arthroscopy”, presentlypending. U.S. application Ser. No. 14/082,855 claimed priority from U.S.Provisional Application Ser. No. 61/751,349, filed in Jan. 11, 2013 andentitled “Shock-Absorbing Implant with Pressure Adjustment and Sensingfor Reverse Shoulder Arthroscopy”. Additionally, U.S. patent applicationSer. No. 14/082,855 claimed priority from U.S. Provisional ApplicationSer. No. 61/727,399, filed in Nov. 16, 2012 and entitled“Shock-Absorbing Implant for Use in Reverse Shoulder Arthroscopy”.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIALS SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to shoulder replacement surgery. Moreparticularly, the present invention the relates to implants that areused in shoulder arthroplasty. More particularly, the present inventionthe relates to a shock-absorbing element incorporated into such implantsso as to avoid the risk of fracture and damage to either the surroundingbone and/or implant.

2. Description of Related Art Including Information Disclosed Under 37CFR 1.97 and 37 CFR 1.98.

Every year, thousands of conventional total shoulder replacements aresuccessfully carried out in the United States for patients with shoulderarthritis. This type of surgery, however, is not as beneficial forpatients with large rotator cuff tears who have developed a complex typeof shoulder arthritis called “cuff tear arthropathy”. For thesepatients, conventional total shoulder replacement may result in pain andlimited motion, and reverse total shoulder replacement may be an option.

A conventional shoulder replacement device mimics the normal anatomy ofthe shoulder. In other words, a plastic cup is fitted into the shouldersocket (glenoid), and a metal ball is attached to the top of thehumerus. In a reverse total shoulder replacement, the socket and metalball are switched. The metal ball is fixed to the socket and the plasticcup is fixed to the upper end of the humerus.

A reverse total shoulder replacement works better for people with cufftear arthropathy because it relies on different muscles to move the arm.In a healthy shoulder, the rotator cuff muscles help position and powerthe arm during the range of motion. A conventional replacement devicealso uses the rotator cuff muscles to function properly. In a patientwith a large rotator cuff tear and cuff tear arthropathy, these musclesare no longer functional. The reverse total shoulder replacement relieson the deltoid muscle, instead of the rotator cuff, to power andposition the arm.

Subsequent to the shoulder replacement surgery, the implant can besubjected to a large variety of forces. In particular, if a patientshould fall, the implant may be subjected to extremely large impactforces. These impact forces have been known to fracture the ball whichis attached to the glenoid. In other circumstances, the scapula canbecome fractured because of an impact. In other circumstances, theconnection between the socket and the humerus can become loosened ordetached. In still other circumstances, the humeral shaft can becomefractured as a result of these forces.

Whenever these forces cause a damage to either the implant or to thebone structure, additional surgery may be necessary. Since the ball isattached to the glenoid, it becomes quite difficult to repair andreplace the ball after installation. As a result, the implant can becomeloosened or nonfunctional. In particular, in shoulder replacementsurgery, repairs to the implant, following the surgery, are quitecomplex. As such, a need has developed so as to provide a shoulderimplant structure which avoids the damage that can occur from sharpimpact forces imparted to the implant.

Shock-absorbing structures have been known to be used in hip replacementsurgery. In particular, a variety of patents have issued relating tosuch shock-absorbing structures. In particular, U.S. Pat. No. 5,201,881,issued on Apr. 13, 1993 to D. L. Evans, shows a joint prosthesis thatprovides articulating prosthesis components that can deflect withrespect to one another so that shock absorption is provided. This servesto lower impact stresses. The components interface at articulatingsurfaces. A gap is provided at a position away from the articulatingsurfaces. As a result, one of the components can flex into the gap areaduring use.

U.S. Pat. No. 5,389,107, issued on Feb. 14, 1995 to Nassar et al.,provides a shock absorbent prosthetic hip implant that includes a socketsection that is attachable to the pelvic bone and a ball section that ispivotably engaged with the socket section. There is a first shockabsorber section attached to the ball section and a second shockabsorber section attached to an upper part of the femur bone. The secondshock absorber section slidably engages the first shock absorbersection. A spring is disposed between the first and second shockabsorber sections for cushioning a compressive force applied between thefemur and pelvic bones.

U.S. Pat. No. 6,336,941, issued on Jan. 8, 2002 to Subba Rao et al.,discloses a modular hip implant with a shock absorption system. Theshock absorption system absorbs compressive stresses that are impartedto the implant. A unique coupling member houses a modular springmechanism that serves as the shock absorber.

U.S. Pat. No. 8,070,823, issued on Dec. 6, 2011 to Kellar et al.,teaches a prosthetic ball-and-socket joint. This ball-and-socket jointincludes first member having a balanced centroidal axis and includes arigid material with a concave interior defining a cup surface. The cupsurface includes a cantilevered first flange defining a wear-resistantprotruding first contact rim. The first flange is asymmetric relative tothe balanced centroidal axis. A cantilevered second flange defines awear-resistant protruding second contact rim. The second member is madeof a rigid material with a wear-resistant convex contact surface. Thefirst and second contact rims bear against the contact surface of thesecond member to transfer loads between the first and second memberswhile allowing pivoting motion therebetween. The flanges are shaped andsized to deform elastically and permit the first and second contact rimsto conform in an irregular shape to the contact surface when the jointis under load.

U.S. Patent Publication No. 2002/0143402, published on Oct. 3, 2002 toA. Steinberg, shows a hip joint prostheses that has at least a first anda second load-carrying member. The first load-carrying member issubstantially more shock absorbing and resilient than the secondload-carrying member.

U.S. Patent Publication No. 2006/0064169, published on Mar. 23, 2006 toB. A. Ferree, discloses shock-absorbing joint and spine replacements. Inparticular, the joint is a total knee replacement. This total kneereplacement implant includes a femoral component having a wheel. Theimplant has a tibial component that includes a shock-absorbing componentwith a piston assembly and spring. The implants contain a cushioning orshock-absorbing member to dampen axial loads and other forces. Fluid isforced rapidly from the device wherein compression and dampening isachieved by valves or other pathways that allow for a slower return ofthe fluid back into the implant as the pressure is relieved.

It is quite natural that shock-absorbing systems have been utilized forknee and hip replacements since the knee and the hip are often subjectedto large impact forces. However, typically, with shoulder replacements,the shoulders are not subjected to such strong forces, unless thepatient should fall or be involved in an accident. As such, in the past,shock-absorbing systems for shoulder replacement implants have not beendeveloped. As a result, under those circumstances where a patient shouldfall or be involved in an accident, extensive surgery can be necessaryso as to repair the implant and/or the surrounding bone structures. Assuch, a need has developed so as to provide a shock-absorbing implantfor shoulder replacement surgery.

U.S. Pat. No. 6,336,941, issued on Jan. 8, 2002 to Subba Rao et al.,shows a modular implant with a shock absorption system. This is amodular implant that can be custom fit to an individual patient. Theshock absorption system absorbs compressive stresses that are impartedto the implant. The size of the femoral ball member, size of the femoralstem, femoral neck length, and tension in the shock absorber system isavailable for all individually adjustable parameters, depending on theparticular patient. A coupling member houses a modular spring mechanismthat serves as the shock absorber. The coupling member is received intothe ball member to an adjustable depth, the adjustment of which variesthe length of the femoral neck.

U.S. Pat. No. 8,591,591, issued on Nov. 26, 2013 to Winslow et al.,discloses a spring base glenosphere. In particular, this is a reversemodular humeral implant for implantation into a humerus that includes anatural humeral shaft and a natural humeral head. The implant includes ahumeral stem implantable into the natural humeral shaft, and an adaptercouplable to the humeral stem. The adapter includes an anchoringprojection configured to be coupled to a convex bearing.

U.S. Pat. No. 5,080,673, issued on Jan. 14, 1992 to Burkhead et al.,describes a glenoid prosthesis and method of use. The glenoid prosthesishas a lateral surface for articulating with the humeral head and a flatmedial surface which engages a flat surface resected from the glenoidcavity. A pair of pegs extend medially from the flat medial surface ofthe glenoid prosthesis which are positioned in a pair of holes and themating flat surfaces and pegs and holes are bonded with cement.

It is quite natural that shock-absorbing systems have been utilized forknee and hip replacements since the knee and the hip are often subjectedto large impact forces. However, typically, with shoulder replacements,the shoulder prostheses are not subjected to such strong forces, unlessthe patient should fall or be involved in an accident. In the past,shock-absorbing systems for shoulder replacement implants have not beendeveloped. As a result, under those circumstances where a patient shouldfall or be involved in an accident, extensive surgery can be necessaryso as to repair the implant and/or the surrounding bone structures. Assuch, a need has developed so as to provide a shock-absorbing implantfor shoulder replacement surgery.

It is an object of the present invention to provide a shock-absorbingimplant which minimizes the transmission of forces to the glenoidportion of the implant or to the humeral head portion of the implant.

It is another object of the present invention to provide ashock-absorbing implant which mitigates micro-forces.

It is another object of the present invention to provide ashock-absorbing implant which creates a weak link such that an easilyrepairable portion of the implant will fail prior to a less easilyrepaired component of the implant.

It is still a further object of the present invention provide ashock-absorbing implant which avoids any fracturing of the bone and/ordamage to the implant.

It is another object of the present invention to provide ashock-absorbing implant which is easily replaceable.

These and other objects and advantages of the present invention willbecome apparent from a reading of the attached specification andappended claims.

BRIEF SUMMARY OF THE INVENTION

The present invention is a shock-absorbing implant for use in shoulderarthroplasty. The shock-absorbing implant comprises a bearing surface, amounting base affixed to or formed with the bearing surface, a convexelement extending outwardly of the mounting base opposite the bearingsurface, a receptacle positioned so as to slidably or pivotably receivea portion of the convex element therein, a housing receiving at least aportion of the receptacle therein, and a resilient element received inthe housing and bearing against a surface of the housing and against asurface of the receptacle.

In the present invention, the bearing surface has a concavity formed ona surface thereof opposite the mounting base. A beam ring is interposedbetween the convex element and the receptacle. The beam ring extendsradially outwardly of the convex element. The beam ring includes acentral ring and a plurality of arms extending radially outwardly of thecentral ring. The plurality of arms bear against a side of the mountingbase opposite the bearing surface. Each of the plurality of arms reducesin width from the central ring toward an outer end of the arm. Also,each of the plurality of arms reduces in thickness from the central ringtoward an outer end of the arm. The central ring has an opening in aninterior thereof. The convex element extends through this opening.

The receptacle has a first portion and a second portion. The firstportion has a concavity formed therein. This concavity receives aportion of the convex element therein. This portion of the convexelement has a convexity with a radius that is less than a radius of theconcavity of the first portion of the receptacle.

The housing has a well formed therein. The well has a first portion anda second portion. The first portion has an inner diameter greater thanan inner diameter of the second portion. The resilient element bearsagainst the first portion of the receptacle. The previously-describedsurface of the housing is a shoulder formed at the bottom of the firstportion of the well of the housing. The second portion of the receptacleis received in the second portion of the housing. Alternatively, theresilient member is received in the second portion of the housing andbears against the first portion of the receptacle. The housing includesa first housing element and a second housing element affixed to thefirst housing element. The second housing element retains the receptaclewithin the first housing element. The convex element extends through awall of the second housing element so as to fit against the concavesurface of the receptacle.

The convex element of the present invention includes a partiallyspherical element and a stem extending outwardly of the partiallyspherical element. The stem has an end opposite the partially sphericalelement that is affixed to the mounting base. The convex element has ajunction portion between the partially spherical element and the stem.The junction portion has a diameter less than a maximum of diameter ofeither of the partially spherical element and the stem.

In the present invention, a plurality of fasteners are affixed to themounting base to the beam ring. Also, in the present invention, theresilient element is a spring. In those circumstances when theshock-absorbing element is a glenoid implant, then the bearing surfaceis concave. In those cases where the shock-absorbing implant is for ahumeral head, the bearing surface is convex.

This foregoing section is intended to describe, with particularity, thepreferred embodiments of the present invention. It is understood thatmodifications to these preferred embodiments can be made within thescope of the present invention. As such, this section is not construed,in any way, as limiting of the broad scope of the present invention. Thepresent invention should only be limited by the following claims andtheir legal equivalents.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side elevational view of the shock-absorbing implant inaccordance with the preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of the shock-absorbing implant of thepreferred embodiment the present invention.

FIG. 3 is an exploded view of the shock-absorbing implant of the presentinvention.

FIG. 4 is an upper perspective view showing the beam ring as used in theshock absorbing implant of the present invention.

FIG. 5 is a cross-sectional view of an alternative embodiment of theshock-absorbing implant of the present invention.

FIG. 6 is an exploded view of the alternative embodiment of theshock-absorbing implant of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is shown the shock-absorbing implant inaccordance with the preferred embodiment of the present invention. Inparticular, the shock-absorbing implant 10 is configured as a glenoidimplant. The shock-absorbing implant 10 includes a bearing surface 12, amounting base 14 affixed to or formed with the bearing surface 12, abeam ring 16 secured to the underside of the mounting base 14 oppositethe bearing surface 12, and a housing 18 positioned below the beam ring16. As will be described hereinafter, the mounting base 14 will supporta convex element such that the convex element extends downwardly. Thereceptacle is positioned within the housing 18 so as to slidably orpivotally receive a portion of the convex element thereon.

In FIG. 1, the bearing surface 12 can have an outer surface 20 thatserves to bear against the humeral head (or the humeral head implant).The outer surface 12 can be a polymeric or elastomeric material, such asTEFLON™. As such, the humeral head or the humeral head implant can bearagainst the surface 20 in a natural and conventional manner. The bearingsurface 12 has a side 22 extending outwardly of the surface 20. As such,the side 22 provides support for the surface 20. The mounting base 14 isaffixed to the bearing surface 12 at the side opposite to surface 20. Assuch, the mounting base 14 can provide strong structural support for thebearing surface 12. The beam ring 16 includes a central ring 24 with aplurality of arms 26, 28 and 30 radiating outwardly therefrom. As such,the central ring 24 will be interposed between the housing 18 and themounting base 14. The arms 26, 28 and 30 radiate outwardly so as toprovide support for the outer periphery of the mounting base 14 and theattached bearing surface 12. The housing 14 includes a first housingelement 32 and a second housing element 34. These housing elements 32and 34 are fitted together, adhesively secured together, or screwedtogether, so as to enclose the receptacle and the convex element thereinas will be described hereinafter.

FIG. 2 shows a cross-sectional view of the shock-absorbing implant 10.In particular, it can be seen that the bearing surface 12 includes aconcavity 40 therein. As stated hereinbefore, this concavity willconform to the humeral head or to the humeral head implant. The mountingbase 14 is secured to the side of the bearing surface 12 opposite theconcavity 40. It can be seen that there is a convex element 42 thatincludes a partially spherical element 44 and a stem 46. There is ajunction 48 between this partially spherical surface 44 and the stem 46.The junction 48 has a diameter that is less than the maximum diameter ofeither the stem 46 or the partially spherical element 44. The stem 46 ofthe convex element 42 is affixed within a receptacle 50 formed into themounting base 14. As a result, the convex element 42 will extendoutwardly from the mounting base 14 opposite to the bearing surface 12.

A receptacle 52 is provided so as to have a concave surface 54 thereon.As can be seen, the partially spherical element 44 of convex element 42resides within the concavity 54. Concavity 54 allows the convex element42 to pivot therein and/or to slidably move therein.

The receptacle 52 includes a first portion 56 and a second portion 58.The second portion 58 extends from the first portion 56 in a directionaway from the convex element 42. A resilient member 60 is positionedwithin the housing 18 so as to bear against the first portion 56. Theresilient element 60 is in the nature of a spring that can wrap aroundan annular portion 62 of the receptacle 52. The resilient element 60will urge the receptacle 52 in a direction toward the convex element 42such that the partially spherical element 44 of convex element 42 willbear against the surface of the concavity 54.

In FIG. 2, the housing 18 includes a first portion 32 and a secondportion 34. The second portion 34 is fitted over the first portion 32 soas to enclose the receptacle 52 within the first portion of housing 18.Suitable fasteners 66 and 68 can be used so as to secure the beam ring16 to the mounting base 14.

FIG. 3 is an exploded view of the shock-absorbing implant of the presentinvention. In particular, FIG. 3 shows the bearing surface 12, themounting base 14, the beam ring 16, the convex element 42, thereceptacle 52, the first housing element 32, the second housing element34, and the resilient element 60.

The bearing surface 12 includes a protrusion 70 that is adapted to besnap-fit within a receptacle 72 formed on the adjacent surface of themounting base 14. Alternatively, and within the concept of the presentinvention, the mounting base 14 can be directly formed with orintegrally attached to the bearing surface 12. As such, the bearingsurface 12 is securely fixed to the mounting base 14.

The mounting base 14 includes holes 74 and 76 therethrough. Holes 74 and76 are configured so as to allow respective fasteners 78 and 80 toextend through the holes 74 and 76 so as to be fitted within therespective holes 82 and 84 of the beam ring 16. Additionally, the endsof the fastener 78 and 80 can threadedly engaged with holes 86 and 88 ofthe second housing element 34. In this manner, the beam ring 16 can besecurely sandwiched between the mounting base 14 and the second housingelement 34.

FIG. 3 shows that there is an opening 90 formed on a side of themounting base 14 opposite the bearing surface 12. This opening 90 willserve to receive the stem 46 of the convex element 42. The stem 46 canextend through an opening 92 in the beam ring 16 such so as to fix theposition of the convex element 42 therein. The junction portion of theconvex element 42 can be in snap-fit relationship with the sides of theopening 92 of beam ring 16.

The partially spherical element 44 of the convex element 42 will extendthrough a hole formed in the top surface of the second housing element34 so as to extend downwardly and fit within the concavity 54 of thereceptacle 52. The resilient element 60 is adapted so as to bear againstthe surface 56 of the receptacle 52 and against a surface 96 of thefirst housing element 32. The receptacle 52 also includes a secondportion 98 that is adapted to be received within a second portion 100 ofa well 102 formed in the interior of the first housing element 32. Assuch, the second portion 98 of the receptacle 52 can securely nestwithin the well 102 of the housing 18. In this manner, the resilientelement 60 can resiliently bear against the receptacle 52 in a securemanner.

FIG. 4 is an isolated view of the beam ring 16. The beam ring 16includes a central ring 106 having a hole 108 formed centrally thereof.A plurality of arms 26, 28, 30 and 110 radiate outwardly incircumferentially spaced relationship from the central ring 106. Boltholes 82, 84, 112 and 114 are formed through the thickness of thecentral ring 106.

Importantly, in FIG. 4, it can be seen that each of the arms 26, 28, 30and 110 has a width that decreases from the central ring 106 to anopposite end of each of the arms. Similarly, each of the arms 26, 28, 30and 110 has a thickness that decreases from the central ring 106 to theouter end of each of the arms. As such, each of the arms is configuredto have greater flexibility at the periphery of the beam ring 16 thanadjacent to the central portion of the beam ring.

Importantly, the present invention offers unique advantages as ashock-absorbing implant. In particular, a rotation of the convex element42 with respect to the concavity 54 is allowed. Additionally, since theconcavity 54 has a radius that is greater than the radius of theconvexity of the convex element 42, a gliding effect is also allowed,along with a small translation relative to these elements. It should benoted that the convex element 42 can swing from side-to-side within theconcavity 54 and also slide from side-to-side within the concavity 54.However, because of the large radius of the concavity 54 and the upwardturned ends of the concavity 54, greater resistance is afforded to thesliding of the convex element 42 as it reaches the outer edges of theconcavity. As such, this effectively restricts the movement of theconvex element 42.

If any impact were to occur to the surface 20 of the bearing surface 12,the shock-absorbing implant 10 of the present invention is able todiffuse such an impact by having small displacements on severalelements. In particular, the arms 26, 28, 30 and 110 of the beam ring 16will flex individually and/or at the same time. The gliding jointmechanism provided between the convex element 42 and the concavity 54 ofreceptacle 52 will redirect the impact toward a single degree of freedom(i.e. translation along a single axis). Additionally, and furthermore,the resilient element 60 (i.e. a spring) will collect the impact energyand restore the system to the original position afterward.

If a shearing action is applied to the implant 10, then the presentinvention includes built-in security in order to secure the preservationof the bone to which the implant is attached. In particular, the glidingjoint mechanism provided between the convex element 42 and the concavity54 of receptacle 52 has a reduced cross-sectional area at the elementconnecting the base plate to the mechanism. This reduction of areasintended to break under shear. This maximizes the potential for bonepreservation. Additionally, each or any of the beams 26, 28, 30 and 110could also bend or break in order to avoid damage to the connected bone.In the event that any of the elements associated with the implant 10were to fail, the replacement would not compromise the bone that is usedto fixate the system.

It should be noted that the clearance provided between the bottom of thesurface 56 of receptacle 52 and the shoulder 96 of the housing 18 allowsfor a single axis translational motion of the spring. This clearancecould be filled with an elastomer, a silicone, or similar materials, inorder to enhance the shock-absorption capabilities of the system. Thisclearance could also be used so as to allow for a fluid to fill it so asto provide a natural damper. The filling liquid could be blood, synovialfluid, or a combination of both.

In the embodiment shown in FIGS. 1-3, the shock-absorbing implant 10 isintended for use as a glenoid implant. In order to properly secure theglenoid implant, the housing 18 can be properly secured by nails orscrews within the bone tissue provided at the glenoid. As such, thesurface 20 of the bearing surface 12 can face outwardly in the directiontoward the humeral head. In certain circumstances, it may be desirableto use the shock-absorbing implant of the present invention inassociation with such a humeral head. FIGS. 5 and 6 illustrate such aconfiguration.

In FIG. 5, there shown the shock-absorbing implant 200 in accordancewith the teachings of the present invention. Shock-absorbing implant 200has a configuration similar to that shown in the previous embodimentexcept for the fact that the bearing surface 12 is actually a convexsurface 202. Convex surface 202 will mimic the surface of the humeralhead. As such, there is a smooth contoured surface 202 that can bearagainst the glenoid or the glenoid implant. A mounting base 204 issecured to the convex bearing surface 202 in the manner described hereinpreviously. A beam ring 206 is affixed to the surface of the mountingbase 204 opposite the convex bearing surface 202. The convex element 208is secured so as to extend to a receptacle 210. Receptacle 210 isreceived within a housing 212.

Unlike the previous embodiment of the present invention, it can be seenthat the receptacle 210 includes a first portion 214 and a secondportion 216. The resilient element 218 is received in the well 220 ofthe housing 212 so as to extend around the second portion 216 and tobear against the first portion 214. In contrast to the previousembodiment, it can be seen that the spring 218 is received within thesmaller inner diameter portion of the well 220 rather than in the largerinner diameter portion of the well. Within the concept of theshock-absorbing implant 200, as shown in FIG. 5, it is also possiblethat the configuration of spring and surfaces of the receptacle could besimilar to that shown in the previous embodiment.

FIG. 6 illustrates an exploded view of the shock-absorbing humeral headimplant 200 in accordance with this alternative embodiment of thepresent invention. In particular, it can be seen that the convex bearingsurface 202 can be affixed to the mounting plate 204 by virtue of theprotrusion 206 that is received within the receptacle 208 formed on themounting base 204. Fasteners 210 extend through the mounting base 204and through holes in the beam ring 212 so as to engage with the secondhousing element 214. The convex element 216 is affixed within theopening 218 of the mounting base 204, extends through the beam ring 212,and has a convex surface bearing against a concavity 220 of thereceptacle 222. The first housing element 224 receives the spring 226within a lower well 228 such that the spring 226 can bear against theshoulder of the receptacle 222. The second housing element 214 can befitted over the male end of the first housing element 224 so as toenclose the receptacle 220 and the spring 226 therein.

In the embodiments of FIGS. 5 and 6, the housing 220 can be affixed, ina conventional fashion, at the humeral head of a humerus. As such, theconvex bearing surface 202 can extend outwardly at a conventional angletoward the glenoid. The humeral head implant 200 can be used inconjunction with an existing glenoid or with the shock-absorbing glenoidimplant 10 of FIGS. 1-3.

Within the present invention, is important to note that the bearingsurface of the shock-absorbing implant can be easily exchanged. If it isdesired to be used as a glenoid implant, then the bearing surface 12 ofFIGS. 1-3 can be used. Alternatively, if the shock-absorbing implant isintended as a humeral head implant, then the convex bearing surface 202of FIGS. 5 and 6 can be utilized. As such, it is easy to adapt theshock-absorbing implant for different purposes. The present inventioncan also be used as a regular shoulder joint replacement or as a reverseshoulder joint replacement. The entire shock-absorbing system isintended to be positioned as near as possible to the joint. However, itshould not be limited to this since it can be actuated by other methodsas well.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof. Various changes in the details ofthe illustrated construction can be made within the scope of the presentclaims without departing from the true spirit of the invention. Thepresent invention should only be limited by the following claims andtheir legal equivalents.

We claim:
 1. A shock-absorbing implant for use in shoulder arthroplasty,the shock-absorbing implant comprising: a bearing surface; a mountingbase affixed to or formed with said bearing surface; a convex elementextending outwardly of said mounting base opposite said bearing surface;a receptacle positioned so as to slidably or pivotably receive a portionof said convex element opposite said mounting base; a housing receivingat least a portion of said receptacle therein, said housing having asurface thereon; and a resilient element received in said housing andbearing against said surface of said housing and against a surface ofsaid receptacle so as to urge said receptacle toward said portion ofsaid convex element.
 2. The shock-absorbing implant of claim 1, saidbearing surface having a concavity formed on a surface thereof oppositesaid mounting base.
 3. The shock-absorbing implant of claim 1, saidbearing surface having a convexity formed on or attached to a surfacethereof that is opposite said mounting base.
 4. The shock-absorbingimplant of claim 1, further comprising: a beam ring interposed betweensaid convex element in said receptacle, said beam ring extendingradially outwardly of said convex element.
 5. The shock-absorbingimplant of claim 4, said beam ring comprising: a central ring; and aplurality of arms extending radially outwardly of said central ring,said plurality of arms bearing against a side of said mounting baseopposite said bearing surface.
 6. The shock-absorbing implant of claim5, each of said plurality of arms reducing in width from said centralring toward an outer end of the arm.
 7. The shock-absorbing implantclaim 5, each of said plurality of arms reducing in thickness from saidcentral ring toward an outer end of the arm.
 8. The shock-absorbingimplant of claim 5, said central ring having an opening in an interiorthereof, said convex element extending through said opening.
 9. Theshock-absorbing implant of claim 1, said receptacle having a firstportion and a second portion, said first portion having a concavityformed therein, said concavity receiving the portion of said convexelement therein.
 10. The shock-absorbing implant claim 9, said portionof said convex element having a convexity having a radius, saidconcavity of said first portion of said receptacle having a radius, theradius of said concavity being greater than the radius of saidconvexity.
 11. The shock-absorbing implant of claim 9, said housinghaving a well formed therein, said well having a first portion and asecond portion, said first portion having an inner diameter greater thanan inner diameter of said second portion, said resilient element bearingagainst said first portion of said receptacle, said surface of saidhousing being a shoulder formed at a bottom of said first portion ofsaid well of said housing.
 12. The shock-absorbing implant of claim 11,said second portion of said receptacle received in said second portionof said housing.
 13. The shock-absorbing implant of claim 9, saidhousing having a well formed therein, said well having a first portionof a second portion, said first portion having an inner diameter greaterthan an inner diameter of said second portion, said resilient elementreceived in said second portion of said housing and bearing against saidfirst portion of said receptacle.
 14. The shock-absorbing implant ofclaim 1, said housing comprising: a first housing element; and a secondhousing element affixed to said first housing element, said secondhousing element retaining said receptacle within said first housingelement, said convex element extending through a wall of said secondhousing element so as to fit against a concave surface of saidreceptacle.
 15. The shock-absorbing implant of claim 1, said convexelement comprising: a partially spherical element; and a stem extendingoutwardly of said partially spherical element, said stem having an endopposite said partially spherical element that is affixed to saidmounting base.
 16. The shock-absorbing implant of claim 15, said convexelement having a junction portion between said partially sphericalelement and said stem, said junction portion having a diameter less thana maximum diameter of said stem.
 17. The shock-absorbing implant ofclaim 4, further comprising: a plurality of fasteners affixing saidmounting base to said beam ring.
 18. The shock-absorbing implant claim1, said resilient element being a spring.
 19. A shock-absorbing glenoidimplant comprising: a concave bearing surface; a mounting base affixedto or formed with said concave bearing surface; a convex elementextending outwardly of said mounting base opposite said concave bearingsurface; a receptacle positioned so as to slidably or pivotably receivea portion of said convex element therein opposite said mounting base; ahousing receiving at least a portion of said receptacle therein, saidhousing having a surface thereon; and a resilient element received insaid housing and bearing against said surface of said housing andagainst a surface of said receptacle so as to urge said receptacletoward said portion of said convex element.
 20. A shock-absorbinghumeral head implant comprising: a convex bearing surface; a mountingbase affixed to or formed with said convex bearing surface; a convexelement extending outwardly of said mounting base opposite said convexbearing surface; a receptacle positioned so as to slidably or pivotablyreceive a portion of said convex element therein opposite said mountingbase; a housing receiving at least a portion of said receptacle therein,said housing having a surface thereon; and a resilient element receivedin said housing and bearing against said surface of said housing andagainst a surface of said receptacle so as to urge said receptacletoward said portion of said convex element.